Heidi, Colin, Audrey and Walter are characters in Gimlet Media's radio thriller Homecoming, about a mysterious government initiative. During season two, running now, Heidi, Colin and Audrey search for project participant Walter Cruz, desperate to discover his state of mind five years after leaving the initiative. As each episode drops, so drops a chapter of The Lost Coast, an ebook written by Homecoming co-creator Eli Horowitz and novelist John Brandon (Citrus County, Further Joy) that follows Walter's progress, internally and up the West Coast.

As Horowitz and co-creator Micah Bloomberg moved forward developing the second season, they found a hole. "Not a plot hole, but an empty space in [the story] that a novel could interestingly fill." The hole had a name: Walter Cruz. The podcast audience listens as the other characters grow increasingly frantic trying to find Cruz. What about letting them read along as Cruz moves forward in time and space? When they realized series sponsor iBooks could provide a platform allowing the novel to be released chapter-by-chapter, they decided to move forward.

Next up, Horowitz contacted Brandon. During his tenure at McSweeney's, Horowitz edited three of Brandon's novels. "He's a real no-nonsense, plugging away writer, not in grim way, he just does it. I knew I could really count on him to do this. He has a specific skill with a certain kind of character who's searching for something, lost souls, that feels genuine but not melodramatic."

Working with the already-established storyline for season two of the podcast, Brandon and Horowitz plotted out Walter's narrative. Horowitz outlined details, figured out priorities, and then handed his notes to Brandon. Early days, the process was less creating, more problem solving.

Trickiest part? Figuring out what to place where. Each podcast episode needed to be followed by a book chapter, which could not mess with an audience's reaction to the next podcast episode. "What took some time was trying to get a sense of what we could tell about Walter. What information we were allowed to present at each spot."

[SPOILER! Go listen. Go read. Now. Then come back to right here.]

For example, in the first few episodes of season two, listeners don't know if Walter is dead or alive. "I didn't want to start in the present day of Walter in the text because that would give it away. It's supposed to be a question. That's why we spent chapter one of the book, a fair bit of it … in his past, before he enlisted. [We performed] little judo tricks to avoid getting ahead of things."

When Horowitz and Bloomberg tackled season one of the podcast, they had to figure out how best to wrangle narrative into an audio-only format. "We can't even have a character be alone. Movement is a hard thing to do in audio. Your internal space is also hard. The best thing for audio I think is immediate empathy. The voice in your ear is very powerful, and the details of how two characters interact with each other. Homecoming is built around those two things."

Returning to text, Horowitz felt — saw — Homecoming open up in new directions. With the podcast, "we were only using Walter when we needed him, and we were only imagining him for his functions," Horowitz explained. "The novel helped us inhabit him in a deeper way, and let us understand him in a better way."

"Solitary movement, internal voice, who [a character is] alone, all of those things are better in prose. It was excited being reminded that … prose has specific fundamental powers that no other form has in quite the same way."

As Walter and The Lost Coast move toward their conclusion, as Homecoming moves towards its season finale, Horowitz is again thinking of the narrative in terms of a new medium. Mr. Robot creator Sam Esmail is teaming up with Horowitz, Bloomberg and other members of the Homecoming team to bring the story to Amazon next year. No word yet on when the TV series will air, though Julia Roberts has signed on to play the on-screen version of Heidi Bergman. Horowitz and Bloomberg are also scheming to bring podcast diehardsseason three.

Join us in celebrating the enormous talent that goes into book cover design. Consider a small donation to our Patreon fund. Your support helps us provide you with an in-depth look at some of the book publishing industry's most creative people.

Susanna previously wrote for the online design community Dribbble, helping transform their occasional blog into the online publication Courtside. Her bylines also include AOL News, Boston Globe, Boston Magazine, and Publishers Weekly, among other publications.